KEYS: Fix __key_link_end() quota fixup on error

Fix __key_link_end()'s attempt to fix up the quota if an error occurs.

There are two erroneous cases: Firstly, we always decrease the quota if
the preallocated replacement keyring needs cleaning up, irrespective of
whether or not we should (we may have replaced a pointer rather than
adding another pointer).

Secondly, we never clean up the quota if we added a pointer without the
keyring storage being extended (we allocate multiple pointers at a time,
even if we're not going to use them all immediately).

We handle this by setting the bottom bit of the preallocation pointer in
__key_link_begin() to indicate that the quota needs fixing up, which is
then passed to __key_link() (which clears the whole thing) and
__key_link_end().

Signed-off-by: David Howells <dhowells@redhat.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/security/keys/internal.h b/security/keys/internal.h
index edfa50d..a52aa7c 100644 (file)
--- a/security/keys/internal.h
+++ b/security/keys/internal.h
@@ -87,13 +87,13 @@ extern void key_type_put(struct key_type *ktype);
 extern int __key_link_begin(struct key *keyring,
                            const struct key_type *type,
                            const char *description,
-                           struct keyring_list **_prealloc);
+                           unsigned long *_prealloc);
 extern int __key_link_check_live_key(struct key *keyring, struct key *key);
 extern void __key_link(struct key *keyring, struct key *key,
-                      struct keyring_list **_prealloc);
+                      unsigned long *_prealloc);
 extern void __key_link_end(struct key *keyring,
                           struct key_type *type,
-                          struct keyring_list *prealloc);
+                          unsigned long prealloc);
 
 extern key_ref_t __keyring_search_one(key_ref_t keyring_ref,
                                      const struct key_type *type,

diff --git a/security/keys/key.c b/security/keys/key.c
index 84d4eb5..1c2d43d 100644 (file)
--- a/security/keys/key.c
+++ b/security/keys/key.c
@@ -415,7 +415,7 @@ static int __key_instantiate_and_link(struct key *key,
                                      size_t datalen,
                                      struct key *keyring,
                                      struct key *authkey,
-                                     struct keyring_list **_prealloc)
+                                     unsigned long *_prealloc)
 {
        int ret, awaken;
 
@@ -481,7 +481,7 @@ int key_instantiate_and_link(struct key *key,
                             struct key *keyring,
                             struct key *authkey)
 {
-       struct keyring_list *prealloc;
+       unsigned long prealloc;
        int ret;
 
        if (keyring) {
@@ -526,7 +526,7 @@ int key_negate_and_link(struct key *key,
                        struct key *keyring,
                        struct key *authkey)
 {
-       struct keyring_list *prealloc;
+       unsigned long prealloc;
        struct timespec now;
        int ret, awaken, link_ret = 0;
 
@@ -814,7 +814,7 @@ key_ref_t key_create_or_update(key_ref_t keyring_ref,
                               key_perm_t perm,
                               unsigned long flags)
 {
-       struct keyring_list *prealloc;
+       unsigned long prealloc;
        const struct cred *cred = current_cred();
        struct key_type *ktype;
        struct key *keyring, *key = NULL;

diff --git a/security/keys/keyring.c b/security/keys/keyring.c
index 92024ed..5620f08 100644 (file)
--- a/security/keys/keyring.c
+++ b/security/keys/keyring.c
@@ -25,6 +25,8 @@
                (keyring)->payload.subscriptions,                       \
                rwsem_is_locked((struct rw_semaphore *)&(keyring)->sem)))
 
+#define KEY_LINK_FIXQUOTA 1UL
+
 /*
  * When plumbing the depths of the key tree, this sets a hard limit
  * set on how deep we're willing to go.
@@ -699,11 +701,11 @@ static void keyring_unlink_rcu_disposal(struct rcu_head *rcu)
  * Preallocate memory so that a key can be linked into to a keyring.
  */
 int __key_link_begin(struct key *keyring, const struct key_type *type,
-                    const char *description,
-                    struct keyring_list **_prealloc)
+                    const char *description, unsigned long *_prealloc)
        __acquires(&keyring->sem)
 {
        struct keyring_list *klist, *nklist;
+       unsigned long prealloc;
        unsigned max;
        size_t size;
        int loop, ret;
@@ -746,6 +748,7 @@ int __key_link_begin(struct key *keyring, const struct key_type *type,
 
                                /* note replacement slot */
                                klist->delkey = nklist->delkey = loop;
+                               prealloc = (unsigned long)nklist;
                                goto done;
                        }
                }
@@ -760,6 +763,7 @@ int __key_link_begin(struct key *keyring, const struct key_type *type,
        if (klist && klist->nkeys < klist->maxkeys) {
                /* there's sufficient slack space to append directly */
                nklist = NULL;
+               prealloc = KEY_LINK_FIXQUOTA;
        } else {
                /* grow the key list */
                max = 4;
@@ -794,8 +798,9 @@ int __key_link_begin(struct key *keyring, const struct key_type *type,
                nklist->keys[nklist->delkey] = NULL;
        }
 
+       prealloc = (unsigned long)nklist | KEY_LINK_FIXQUOTA;
 done:
-       *_prealloc = nklist;
+       *_prealloc = prealloc;
        kleave(" = 0");
        return 0;
 
@@ -836,12 +841,12 @@ int __key_link_check_live_key(struct key *keyring, struct key *key)
  * combination.
  */
 void __key_link(struct key *keyring, struct key *key,
-               struct keyring_list **_prealloc)
+               unsigned long *_prealloc)
 {
        struct keyring_list *klist, *nklist;
 
-       nklist = *_prealloc;
-       *_prealloc = NULL;
+       nklist = (struct keyring_list *)(*_prealloc & ~KEY_LINK_FIXQUOTA);
+       *_prealloc = 0;
 
        kenter("%d,%d,%p", keyring->serial, key->serial, nklist);
 
@@ -881,20 +886,22 @@ void __key_link(struct key *keyring, struct key *key,
  * Must be called with __key_link_begin() having being called.
  */
 void __key_link_end(struct key *keyring, struct key_type *type,
-                   struct keyring_list *prealloc)
+                   unsigned long prealloc)
        __releases(&keyring->sem)
 {
        BUG_ON(type == NULL);
        BUG_ON(type->name == NULL);
-       kenter("%d,%s,%p", keyring->serial, type->name, prealloc);
+       kenter("%d,%s,%lx", keyring->serial, type->name, prealloc);
 
        if (type == &key_type_keyring)
                up_write(&keyring_serialise_link_sem);
 
        if (prealloc) {
-               kfree(prealloc);
-               key_payload_reserve(keyring,
-                                   keyring->datalen - KEYQUOTA_LINK_BYTES);
+               if (prealloc & KEY_LINK_FIXQUOTA)
+                       key_payload_reserve(keyring,
+                                           keyring->datalen -
+                                           KEYQUOTA_LINK_BYTES);
+               kfree((struct keyring_list *)(prealloc & ~KEY_LINK_FIXQUOTA));
        }
        up_write(&keyring->sem);
 }
@@ -921,7 +928,7 @@ void __key_link_end(struct key *keyring, struct key_type *type,
  */
 int key_link(struct key *keyring, struct key *key)
 {
-       struct keyring_list *prealloc;
+       unsigned long prealloc;
        int ret;
 
        key_check(keyring);

diff --git a/security/keys/request_key.c b/security/keys/request_key.c
index 9a7fb39..a3dc0d4 100644 (file)
--- a/security/keys/request_key.c
+++ b/security/keys/request_key.c
@@ -352,8 +352,8 @@ static int construct_alloc_key(struct key_type *type,
                               struct key_user *user,
                               struct key **_key)
 {
-       struct keyring_list *prealloc;
        const struct cred *cred = current_cred();
+       unsigned long prealloc;
        struct key *key;
        key_ref_t key_ref;
        int ret;